Cerebral columnar organization of the first nociceptive component induced by CO2 laser on the tail of the rat.
The somatotopic map of the first nociceptive component in the primary somatosensory cortex (S1) is still unclear. In this study, a CO(2) laser was applied to the tail of the rat to induce nociception without the interference from large myelinated (A(beta)) fibers. Thus, only noxious fibers could be activated. Two-dimensional current-source-density analysis was used to analyze the evoked field potentials. Using this method, the nociceptive responses of A(delta)-fibers in S1 were verified, and the somatotopic map of the first nociceptive component in S1 was identified. We found that whether light touch or laser-induced nociception was applied to the tail of the rat, the responsive topography in S1 was consistent. Discrimination of these two modalities was achieved vertically in the same column; the deeper layer represented the nociceptive response while the superficial layer encoded the response to light touch. This is quite different from that of a primate brain.
Jaw
F-S
FS
Institute of Biomedical Engineering, National Taiwan University, No.1, Sec. 4, Roosevelt Rd., Taipei 10617, Taiwan. jaw@ntu.edu.tw
Kao
Y-C
YC
Chen
C-P
CP
Liao
W-L
WL
D000818:Animals; D001931:Brain Mapping; D004569:Electroencephalography; D005073:Evoked Potentials, Somatosensory / Q000528:radiation effects; D054020:Lasers, Gas / Q000009:adverse effects*; D008297:Male; D009413:Nerve Fibers, Myelinated / Q000502:physiology; D009431:Neural Conduction / Q000528:radiation effects; D010146:Pain / Q000209:etiology* / Q000473:pathology*; D010147:Pain Measurement; D010812:Physical Stimulation / Q000379:methods; D051381:Rats; D017208:Rats, Wistar; D011930:Reaction Time / Q000187:drug effects; D013003:Somatosensory Cortex / Q000503:physiopathology*; D013623:Tail / Q000294:innervation / Q000528:radiation effects*